The present invention relates to a method of and an arrangement for adjusting of three rollers or guiding rollers which together form a caliber opening.
In rolling stands for rolling wires, bars and pipes the caliber openings which are formed by rolling elements such as rollers or guiding rolls must be made with the accurate size and shape to provide the required narrow size tolerances and the desired high shape accuracy of the rolled products. This first of all is true for the last caliber opening or openings of a rolling path. For obtaining this accuracy also for a caliber opening which is formed by three rollers or guiding rolls, the working surfaces of the rollers or the guiding rolls which come into contact with the rolled product are machined in condition ready for operation when they are built in the rolling stand or guiding housing. This process, however, is very expensive. Moreover, the desired accuracy is not always achieved. This is especially true when it is not possible to provide chip-removing working inside the caliber opening. In contrast, the outer contours of the rollers or guiding rolls can be produced in quieter and more accurate fashion individually in disassembled condition on precision-operating machine tools. In this case rollers with accurate profiles can be obtained, formed from the working and edge surfaces as well as the transition radii. However, also no accurate caliber opening is guaranteed. In order to provide this, it is additionally necessary to exactly adjust the rollers or the guiding rolls relative to one another, since with the abutment surfaces, fixed supports and similar elements it cannot be guaranteed that each roller or guiding roll after its production in disassembled condition and subsequent assembly assumes the exactly predetermined position. Each roller or guiding roll after its assembly, must be adjusted in an axial direction, or in other words in the direction of the rotary axis of the rollers, must be also adjusted in a radial direction. The bearing permits such an adjustment.
The invention deals with a method of adjusting of three rollers or guiding rolls which together form a caliber opening, which are offset in a star-like fashion around a throughgoing axis which forms a center of a caliber opening, and which have concavely shaped working surfaces. The method can also be used for adjusting of five or more rollers or guiding rolls which form a caliber opening which hardly happens in practice.
In accordance with the known method of this type, a light source is arranged at one side of the caliber opening, while at the other end a device is arranged which receives the shadow image around the caliber opening and can recognize its contours. Such device can be formed, for example, as a ground glass. As a rule, an amplifying optical system is arranged between them to obtain a clear shadow image. On it, the limits of the caliber opening are recognized by the working surfaces, for example, of the rollers as well as small roller gaps which remain between the facing inclined edge surfaces of the neighboring rollers. Also the transition radii between the working surfaces and edge surfaces are recognizable. A bar template is applied on the ground glass which indicates the shadow image. For adjusting the rollers of a three roller caliber it is marked with three ray lines which extend in radial direction from one another from one point in a star-like fashion and offset relative to one another by 120.degree. in correspondence with the conventional 120.degree. arrangement of the rollers of the three roller caliber. The bar template is applied in the known method on the ground glass so that each of the three ray lines comes to abutment in the center of one of the three roller gaps of the shadow image. The intersecting point of the ray lines marks then the center of the caliber opening. Starting from this caliber center, the contours of the caliber opening can then be worked or controlled and the rollers of the guiding rolls can be adjusted in the radial direction.
This known method is, however, inaccurate and can be implemented only with difficulties when the roller gaps shown on the shadow image have different widths as frequently occurs. The reason for this can be that the rollers have different diameters. Moreover, the rollers are often arranged displaceably in an axial direction. Furthermore, the inclined edge surfaces of the rollers formed between the roller gaps at the concave working surfaces can have an offset, since the edge surfaces are not always worked together with the working surfaces. In these frequently occurring cases it is extraordinarily difficult, if not impossible, to exactly orient the bar template with the above described methods, in order to determine in this manner the position of the caliber center. If it is not or cannot be sufficiently accurately determined, an accurate adjustment of the rollers or guiding rolls of the caliber is not possible.
The caliber center is a geometrical center of the caliber opening formed by the working surfaces of three rollers or guiding rolls. It does not necessarily coincide with the rolling stand center or with the center of the inscribed circle of each triangle which forms the rotary axes of the rollers. Therefore, when for example, the diameters of the three rollers or guiding rolls which form a caliber are not uniform due to different wear or manufacturing inaccuracies, the caliber center is located in a point different from the center of the rolling stand. Thus, for determination of the caliber center one cannot go from the center of the rolling stand or the center of the guiding rolls housing and also not from the measuring surfaces, since during the mounting and dismounting of the rollers always certain displacements occur. For the same reason the rotary axes of the rollers or guiding rolls are not suitable as orienting lines for the adjustment. Also, one cannot go from the edge surfaces of the rollers of the guiding rolls due to the possibility of an offset between them and the working surface contours. Therefore, with the extremely high manufacturing accuracy of the rollers, the guiding rollers, the bearings, the stand and the guiding housing, the desired high accuracy could not be achieved even with extremely high costs.